bi amp imrpoving?

A small but important qualification to Zaikesman's post:

This is of course in addition to the other theoretical benefits [of passive biamping], like doubling the available amp power (assuming the top and bottom amps are identical).

This is a common misconception. In general, passive biamping cannot be expected to double the available power (which is only a 3db increase anyway), or to even come close to doubling the available power.

The amount of power that can be delivered to the speakers is most commonly limited by clipping, i.e., by the amplifier being asked to swing its output voltage to a level that is greater than it is capable of swinging. Since in a passively biamped configuration both amps are being fed full-range signals, the output voltage range they are required to swing will be no different than it would be in a single-amped configuration.

***AN IMPORTANT IMPLICATION OF THIS: If in a passively biamped configuration a low powered tube amp is used on top (for example), and a high powered solid state amp on the bottom, most of the power capability of the high powered amp will be unavailable and wasted. The power capability of the high powered amp that can be utilized will be limited by the clipping point of the low powered amp.***

Passive biamping will only result in an increase in available power to the extent that the internal voltage rails of the amps increase as a result of reduced current demand, and/or to the extent that power delivery of the single-amped configuration that is being compared to is limited by current capability, not voltage swing capability.

Regards,
-- Al

Hi Zaikesman,

I am in complete agreement with nearly all of your comments. And I certainly agree with the fundamental point that passive biamping, if well implemented, can yield significant sonic advantages along the lines that you and others have described.

However, I have seen several instances in the past in which the misconception I commented on nearly led to purchase decisions that would have been major mistakes.

Restating my basic points by way of examples:

1)Under typical circumstances, passively biamping two 50 watt amplifiers will result in little more than the equivalent of a single 50 watt amplifier, in terms of the peak volume level that can be generated.

2)Under typical circumstances, passively biamping a 50 watt amplifier with a 500 watt amplifier(!) will also result in little more than the equivalent of a single 50 watt amplifier (sic), in terms of the peak volume level that can be generated.

Best regards,
-- Al

At the risk of repeating myself or seeming a jerk, IMHO the peak volume level that can be generated is largely beside the point.... Where distortion isn't perceived as a negative, ear-splitting levels can be achieved with relatively "low" wattage, as proved by my 40w Fender Super Reverb 4 x 10" tube guitar amp.)

That is true if the music has little dynamic range (meaning the difference in volume between the loudest notes and the softest notes). Most rock recordings fall into that category.

However, for music with wide dynamic range, such as well recorded, minimally compressed classical symphony orchestra, peak volume capability is most definitely not beside the point. On that kind of recording, power requirements for brief peaks can often be literally 1000 times or more as many watts as for the average volume level within the same work, which would correspond to a peak-to-average ratio of 30db.

Best regards,
-- Al